Navieulacea.'] infusorial animalcules. 381 



with two to tlirec median circles ; tlie two tcstules conucctcd by a 

 very wide central band, and by their apices ; thc^opening (hiatns) 

 on each side the band large, and sub-orbicnlar. Diameter l-588th. 

 Vii-ginia Named after Dr. Eogers, the discoverer. 



GoNioTHECiuM (?) dkhjnium. — Testides binate, smooth, trans- 

 versely oblong, obtuse ; emarginate at the centre on one side; on the 

 other with two tubercles. Diameter 1-1 200th. Virginia. 



G. Gastridium. — Testiiles binate, smooth, transversely oblong, 

 ti-uncate at each end, abrubtly dilated at the middle of the ventral 

 surface, but not contiguous. Diameter 1 -960th Virginia. 



G. hispidmn. — Testules binate ; each semi-lunar and hispid, with 

 a tuberosity (umbo) on the inner side at the centre ; the halves 

 contiguous. Diameter 1-1 728th. Vii'ginia. 



G. monodon. — Binate, smooth ; each half linear-oblong, trimcate at 

 each end ; outer side uniformly straight, the internal with a median 

 tuberosity, not contiguous. 



G. (?) Navicula. — Smooth, small, binate, oblong, and rather turgid, 

 ti'uncate at each end. I have not yet observed a median connecting 

 tuberosity. Length l-1680th. Virginia. 



G. obsusuni. — Binate, smooth ; each testule transversely oblong, 

 obtusely tri-lobed ; no connefecing band. Diameter l-696th. 

 Yii'ginia. 



G. Odontella. — Binate, smooth; each testule transversely oblong ; 

 dorsally semilunar or gently angular ; laterally oblong, navicular, 

 mth three concentric circles ; the halves conjoined by the central 

 band and by their apices ; the aperture on each side oblong, con- 

 tracted at the middle. Diameter 1 -480th. to l-276th. Virginia. 



G. crenatum. — Specific characters unknown. (P. 24, fig. 10, 

 represents apparently a semi-frustule.) 



Genus GEAMiLiTOPnoEA (Ehr.) — Lorica bivalved, prismatic ; self- 

 division imperfect ; the cluster ciu-ved ; joints gaping at one of the 

 angles. Within are two septa, dividing the body into three longi- 

 tudinal portions. Marine. 



The form of this genus recals that of Tahellaria, with two internal 

 siliceous folds (^ septa or \'itta^) which are remarkable in being cui'ved 

 after the manner of letters. 



